Getting Ready for Spring
We all look forward to the warm weather, clear skies and spring flowers. We can once again open windows in the morning and late evening, letting fresh air in, thus providing adequate ventilation.
But spring also brings an increase in mold and allergens like pollen from outside air. Furthermore, we will be spending more time outdoors so we will be exposed to these allergens. It is important therefore, that the time we spend indoors is in a clean and healthy environment.
What Scientists tell us about Spring Health Risks
In addition to pollen and mold spores, springtime also brings less known dangers. A report by Daniel Jaffe, et al., published in the Geophysical Research Letters  shows that during spring there is an increase of background levels of ozone on the west coast of North America. This report shows that ozone in air arriving from the Eastern Pacific in the spring has increased by approximately 30% from the mid 1980s to the present
The elevated levels of ozone are a concern since when combined with small particles in the air, PM2.5, they affect the respiratory system. A Study of the Effects of Low-Level Ozone and Fine Particles on the Respiratory Symptoms in Children with Asthma by Janneane F. Gent et al.., published by the American Medical Association , concludes that simultaneous exposure to ozone and fine particles contribute to increase respiratory symptoms and the need for rescue medication use.
It is also known that Mold Allergy problems increase in the spring. Furthermore, studies show that risk of death from asthma during the pollen season is related to the level of Environmental Molds . All the above risks suggest that we should remain vigilant and minimize indoor air pollution. Indoor Air Quality in our homes is our individual responsibility.
What should we do to insure Healthy Indoor Air in the Spring ?
We have discussed in other articles  that the science of clean air is still evolving. There is no scientific consensus on what constitutes “clean air “. Most of the standards are based on “perceived air quality”. Perceived Air Quality (PAQ) is the statistical average of the subjective assessments of air quality by those living in a home or working in a business environment.
Nevertheless, there are common sense actions we can take to improve our Indoor Air Quality (IAQ).
Eliminate Fine Particles (PM2.5) from indoor air
PM2.5 particles are those smaller than 2.5 micrometers. It is especially important to eliminate the ultra fine particles (smaller than .1 micrometers) since these ultra fine particles can translate from lungs to the blood system.Note: Definition of these particles and a discussion of the health risks posed by indoor air pollution can be found in Reference .
Do Not Smoke Indoors
Eliminate Volatile Organic Compounds (VOC’s)
These include fragrances, formaldehyde and other emissions from building materials and furniture. According to a Danish Building Standard the amount of VOC’s should be below levels that can be sensed by the occupants.
Monitor Carbon Dioxide (CO2)
Carbon Dioxide levels to be kept below 1000ppm. Must have Carbon Monoxide detectors since malfunctioning furnaces can be lethal.
Homes should be ventilated as a minimum at a rate of 7.5 cfm(cubic feet per minute) per person plus 3 cfm per 100 square feet of home size. Standards assume that number of home occupants will be equal to the number of bedrooms plus one. As an example a 2000 square feet home, with 2 bedrooms, would require a minimum of 82.5 cfm. 
Humidity should be approximately 35% RH in winter months and 50% RH in the summer.
Air Filters in the Air Conditioning System should be checked and replaced regularly. The Air Filters used should have a Minimum Efficiency Reporting Value (MERV) of 13. This quality filters remove at least 50% of the o.3- 1 micrometer particles.(These are the particle sizes that are most harmful to human health). The best filters, however, are the High Efficiency Particulate Air (HEPA) Filters. These filters are equivalent to a MERV 16 and remove 99% of particles. 
European Standards recommend that air should be supplied to the occupants cool and dry. In addition, the clean air should be introduced close to the breathing zone of each individual. Air Purifiers in the proximity of the occupants should be used. Or at least in the kitchen, living room and bedrooms where many of the indoor pollutants originate.
Implementing the above recommendations will result in Clean and Healthy Indoor Air in all seasons.
Remember,Indoor Air Quality in our homes is our individual responsibility.
 Daniel Jaffe, et al.., Increasing background ozone during spring on the west coast of North America, Geophysical Research Letters / Volume 30, Issue 12
 Janneane F. Gent et al.., Association of Low-Level Ozone and Fine Particles With Respiratory Symptoms in Children with Asthma, American Medical Association, JAMA, October 8, 2003- Vol 290, No.14
 Paul V.Targonski, et al..,Effect of environmental molds on risk of death from asthma during the pollen season, The Journal of Allergy and Clinical Immunology, Volume 95, Issue 5,Pages 955-961